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Convert concentration to dose? 
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#1
Feb1710, 10:16 AM

P: 30

How do you get from a concentration to an effective dose? For example, if you have 10^{9} Ci/cm^{3} of tritium in a human body, then how do you get the effective dose to that body?
Thanks 


#2
Feb1710, 11:39 AM

P: 28

Using the Mass Activity Calculator in Nucleonica (www.nucleonica.net), 10^{9} Ci of tritum corresponds to 37 Bq. Also from Nucleonica, the effective dose coefficient for ingestion for tritium is 1.8x10^{11} Sv/Bq. Hence the dose is 37 x 1.8x10^{11 }Sv per cm^{3} = 57 x 10^{11 }Sv per cm^{3}. To obtain the total dose you then need to multiply by the volume of the human body or that part which has been exposed I'll leave this as an exercise! If the tritium intake is by inhalation, then the effective dose coefficient for inhalation must be used. This is 2.6x10^{10} Sv per Bq i.e. considerably higher than that for ingestion.



#3
Feb1710, 12:33 PM

P: 30

I'm not sure I follow how time plays into this. Does this process give me the Sv per second or per disintegration? If you have a decaying source, you wouldn't just get a single dose. I guess what I'm looking for is the dose rate, sorry for the confusion.



#4
Feb1710, 12:54 PM

Admin
P: 21,869

Convert concentration to dose?



#5
Feb1810, 12:02 PM

P: 28

Dose (Sv) = e(50) x Activity (Bq) From this value one can estimate the risk of cancer for example. Basically the unit Sievert (Sv) is the energy deposited in the tissue. If you would like to calculate the dose rate this requires a different approach. From the activity in Bq, one obtains the number of disintegrations per second. In each disintegration, a 20 keV electron is emitted. This electron is then absorbed in the tissue causing damage. So the rate of energy released is Energy emission rate (keV/s) = Activity (Bq) x 20 keV with units keV per second. This needs to be converted into joules i.e. Energy emission rate (Joule per second) = activity x 20 x 1000 x 1.6e19 For the activity of 37 Bq, this corresponds to Energy emission rate (joule per second)= 37 x 20 x1000 x 1.6e19 = 1.2 E16 Since the "quality factor" for electrons is one, this means that the dose rate is equal to the energy emission rate i.e. Dose Rate = 1.2 E 16 Sieverts per second. This is an extremely small dose rate. For further information, I refer you to the relevant Nucleonica wiki article... http://www.nucleonica.net/wiki/index..._%26_Shielding 


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